Do you realise that people judge credibility through integrity?
No it is not that, in forums people lump together upon same ideas and biases, if you go to Indian forums you will find french and Indian posters saying Rafale has even better features than F-35.
In reality, things are much more complex, just see this i am old enough to have followed Su-27 career, in the 1980s, it was always underestimated, by 1999, it became a really impressive aircraft in the eyes of the public opinion, now in 2015 is a classic Soviet jet fighter in the same league as MiG-21.
If you know aircraft history for at least 35 years, you will know both east and west are engaged in a propaganda campaign.
A war machine is judged upon many factors, not a single parameter.
For example is a fact MiG-23 was armed with BVR missiles in 1980 while F-16 only carried AIM-9s, see history and you find the Russians always claimed the F-16 in 1980 was no match to MiG-23 in BVR, although in close combat it was much superior.
Some historians in Russia will even claim MiG-23MLD flown properly was even a match for F-15 in BVR combat.
Same is now to judge both programs F-35 and PAKFA is very hard because one, they are new, they have no combat experience, thus how effective they are is hard to judge.
In my personal opinion, MiG-23 was no worse than F-4E because both aircraft were downed in large numbers and both aircraft were quiet similar in aerodynamics, technology and producitability.
Same is PAKFA, you always will find western historians saying is not that good, but same F-35, it is belittled in Russia, how good are they, only history will tell.
When you find historians from both sides saying the same then you can get a glimpse of Reality, in Russia the F-15 is respected, if it is compared to MiG-23 or even MiG-21, they admit that F-15 was effective downing them, but when it comes to MiG-29 or MiG-25 they say F-15 was not that good and you can read Russian historians saying MiG-25 downed F-15s and MiG-29s downed Tornadoes and many western fighters in 1991, and compared to Su-27 they say it is inferior, once a US pilot told me Su-27 is a pretty good machine compared to F-15 so both sides agree in some points.
time will tell, but it passes so slow, now aircraft have very long operational careers and development periods just look at MiG-21, it still flies and in new versions it is true is kind of a little challenge to even F-15s.